MRI

Accurate diagnosis relies on obtaining information and piecing it together to obtain

what is usually a ‘best guess’. In medicine, this will always be the case to a greater or

lesser extent as everyone is different, and not all symptoms of the same disease

present in the same way. It is surprising how often people with a clear case of arthritis

can be treated for months for something completely different such as muscle strains

or back pain.

Therefore we like to get the most information about you as we can, and make sure that

what we get is as accurate as it can be. Most MRI scanners, for instance, are termed 1.5

Tesla. This refers to the strength of the magnet that the scanner has. The magnet in the

scanner is used to align water in your body, which ‘spins’ as the magnet is turned on and

off (as water is a charged particle). As the water particles spin, they give of a signal, which is what the scanner detects. Depending on where that water is and what it is part of, determines how quickly it will spin and therefore affects the signal the water gives off. It’s very complicated! However, in simple terms, the stronger the magnet, the more spin, and therefore the stronger signal. This leads to clearer scans, which helps give a more accurate diagnosis.

Historically, to diagnose a labral tear accurately in a 1.5T scanner, you would need a doctor to inject your hip joint with a large volume dye prior to the scan (termed an arthrogram). This is because the clarity of the scans from a 1.5T scanner tends to be poor (around the hip) and the dye gives a better contrast. The arthrogram is performed under local anaesthetic, but the vast majority of patients who have had this done do not wish for another, as it can be quite uncomfortable. However, some people still consider this technique the ‘gold standard’.

Even so, MRI arthrograms have been reported to have a few problems. One is that they can ‘over-call’ labral tears (as in suggest there is one present when there is not). The other is that generally they tend to be very dark scans, which means that the doctor cannot look at the other muscles and structures around the joint which can also be implicated in your pain, it purely looks at the labrum.

With the introduction of 3 Tesla MRI scanners, the arthrogram is no longer needed as the clarity of the scans is so much better. This means a faster visit to the hospital, no injection or pain, and in fact more information as all the surrounding hip structures can be assessed as well.

Cartilage Mapping

Scanning technology has advanced to a point where we can not only see the amount of cartilage that is present in the joint, we can also get an idea of the quality and health of it! There are a few ways of doing this, the original being termed dGEMRIC (delayed Gadolinium Enhanced MRI of Cartilage). This requires an intravenous injection of contrast (Gadolinium). The patient then walks around for 20-45 minutes and then has their scan. It is very time consuming and the intravenous injection can be an issue if you have kidney problems. Therefore, other techniques have been developed; the best one (in our view!) is T2 cartilage mapping. This does not require injections of any sort, although it does add approximately 5 minutes to your scan!

Although all of these techniques are still termed ‘experimental’ the information from the cartilage mapping helps us determine the health of your joint and the areas that may be more damaged than others. This helps the surgeon give you a more accurate prognosis about what may or may not be achieved by various surgical options.

MRI Based T2 Mapping

CT & MOTION ANALYSIS

Many different factors, and often combinations of pathologies, can cause hip pain.

Our job is to unpick these so that we can help get you on the road to recovery. These,

as mentioned throughout our website, rely on accurate diagnosis. Most sports injuries

related to the hip joint such as labral tears are secondary to mild developmental

(shallow hip socket). These can be difficult to diagnose with plain x-rays and even

MRI scans.

Currently, the best way to look at the shape of the bones is CT (computerised

tomography) scans, from which you can get 3D reconstructions. This is like looking

at your skeleton and is a fantastic way of assessing the way the actual joint is formed.

However, things have moved on even further. From the CT scans we can see the way your hip actually moves by sending the scans off for ‘Motion Analysis’. We work with Clinical Graphics in Holland, who specialise in breaking the scans down and rebuilding them showing us how your hip moves. This can demonstrate areas of impingement or dysplasia graphically, both helping you understand your own body, but also demonstrating where the bones should be reshaped to ensure accurate surgery and the best results.

There is a possible downside though. Like x-ray, CT does expose the patient to radiation. However, the current dose from our protocol is estimated to be the equivalent of three x-rays and so is very low. But attempting to keep this to an absolute minimum, Clinical Graphics are working on obtaining the same type of report from MRI scans. This does require specific sequences and can be harder to process. Currently, we believe the CT route to be more accurate, but are working with Clinical Graphics to help improve the MRI-based reports. It is available at the Wellington if you would prefer.

The hip joint and surrounding structures all share nerve supplies. As a result, hip pain can be felt in various different ways, classically in the groin, but commonly the thigh, knee and laterally. It is common to see misdiagnosis as a result. There are numerous other causes of 'hip pain', which have nothing to do with the hip at all! Also, many studies have shown that labral tears can be present in 'normal' patients with no hip problems. Those with hip injuries often develop muscle imbalances, which can be difficult to overcome due to pain inhibition.

We use intra-articular injections to help pin-point the source of the problem, but also to help patients and therapists work through the muscle imbalance issues giving them a 'pain-free window' to work in.